SCSI negotiation problems, please help!

[FreeBSD Questions]

I have a tape drive that seems to have lost its ability to negotiate
optimal settings.

FreeBSD 5.4-Stable (compiled 13 Sep 2005)
Dell PowerEdge 1750

# uname -a
FreeBSD hr-stc-file2.smartrafficenter.net 5.4-STABLE FreeBSD
5.4-STABLE #0: Tue Sep 13 22:44:46 EDT 2005    
root@:/usr/obj/usr/src/sys/HR-STC-FILE2  i386

(from /var/run/dmesg.boot)
ch0 at ahc0 bus 0 target 0 lun 0
ch0: <EXABYTE VXA 1x10 1U A10A> Removable Changer SCSI-4 device
ch0: 80.000MB/s transfers (40.000MHz, offset 32, 16bit)
ch0: 10 slots, 1 drive, 1 picker, 0 portals
...
sa0 at ahc0 bus 0 target 1 lun 0
sa0: <EXABYTE VXA-2 2109> Removable Sequential Access SCSI-2 device
sa0: 80.000MB/s transfers (40.000MHz, offset 32, 16bit)

# camcontrol negotiate ch0
Current Parameters:
(pass1:ahc0:0:0:0): sync parameter: 0
(pass1:ahc0:0:0:0): offset: 0
(pass1:ahc0:0:0:0): bus width: 8 bits
(pass1:ahc0:0:0:0): disconnection is enabled
(pass1:ahc0:0:0:0): tagged queueing is disabled

# camcontrol negotiate sa0
Current Parameters:
(pass2:ahc0:0:1:0): sync parameter: 0
(pass2:ahc0:0:1:0): offset: 0
(pass2:ahc0:0:1:0): bus width: 8 bits
(pass2:ahc0:0:1:0): disconnection is enabled
(pass2:ahc0:0:1:0): tagged queueing is disabled

No matter what I do with camcontrol, I can't get it to change these
parameters--only the user parameters (-U):

#  camcontrol negotiate ch0 -a -c -D enable -O 32 -R 40.000 -T disable -W 16
Current Parameters:
(pass1:ahc0:0:0:0): sync parameter: 0
(pass1:ahc0:0:0:0): offset: 0
(pass1:ahc0:0:0:0): bus width: 8 bits
(pass1:ahc0:0:0:0): disconnection is enabled
(pass1:ahc0:0:0:0): tagged queueing is disabled
New Parameters:
(pass1:ahc0:0:0:0): sync parameter: 0
(pass1:ahc0:0:0:0): offset: 0
(pass1:ahc0:0:0:0): bus width: 8 bits
(pass1:ahc0:0:0:0): disconnection is enabled
(pass1:ahc0:0:0:0): tagged queueing is disabled

# camcontrol negotiate sa0 -a -c -D enable -O 32 -R 40.000 -T disable -W 16
Current Parameters:
(pass2:ahc0:0:1:0): sync parameter: 0
(pass2:ahc0:0:1:0): offset: 0
(pass2:ahc0:0:1:0): bus width: 8 bits
(pass2:ahc0:0:1:0): disconnection is enabled
(pass2:ahc0:0:1:0): tagged queueing is disabled
New Parameters:
(pass2:ahc0:0:1:0): sync parameter: 0
(pass2:ahc0:0:1:0): offset: 0
(pass2:ahc0:0:1:0): bus width: 8 bits
(pass2:ahc0:0:1:0): disconnection is enabled
(pass2:ahc0:0:1:0): tagged queueing is disabled

# camcontrol negotiate sa0 -U
Current Parameters:
(pass2:ahc0:0:1:0): sync parameter: 10
(pass2:ahc0:0:1:0): frequency: 40.000MHz
(pass2:ahc0:0:1:0): offset: 32
(pass2:ahc0:0:1:0): bus width: 16 bits
(pass2:ahc0:0:1:0): disconnection is enabled
(pass2:ahc0:0:1:0): tagged queueing is disabled

I've tried everything I can except a reboot, but that can't happen
right now as this is on a production server.  I've tried rescanning
the bus; I've tried resetting the bus; I've tried powering the
library/drive off, rescanning the bus to remove the devices, powering
the library/drive back on, and rescanning again to find the devices
again; and no matter what I do, I keep getting these 3.3 MB/s transfer
rates, 8-bit bus widths, and very degraded tape performance.  Short of
a reboot, how do I restore the initial negotiation settings from when
the server was initially powered up?

And because I feel like the question is going to be asked... I think
this happened when a coworker cycled power on the tape library.  Is
there any way to reinitialize the SCSI card and renegotiate with the
attached devices?

dmesg.boot and kernel config attached.

Thanks!
Kevin
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